Notifications for when someone posted a comment on your node
was not created.
Root cause was that default values defined in schema was not set,
resulting in activity subscriptions not being active.
There were 2 bugs preventing them to be set:
* The way the caching of markdown as html was implemented caused
default values not to be set.
* Eve/Cerberus regression causes nested default values to fail
https://github.com/pyeve/eve/issues/1174
Also, a 3rd bug caused nodes without a parent not to have a
subscription.
Migration scripts:
How markdown fields is cached has changed, and unused properties
of attachments has been removed.
./manage.py maintenance replace_pillar_node_type_schemas
Set the default values of activities-subscription
./manage.py maintenance fix_missing_activities_subscription_defaults
Custom types became rather useless in Cerberus 1.0 since the type checker
is cripled (doesn't know field name, cannot return useful/detailed error
messages). Instead we use a validator now.
